Wafer scale packaging platform for transceivers

ABSTRACT

A wafer scale implementation of an opto-electronic transceiver assembly process utilizes a silicon wafer as an optical reference plane and platform upon which all necessary optical and electronic components are simultaneously assembled for a plurality of separate transceiver modules. In particular, a silicon wafer is utilized as a “platform” (interposer) upon which all of the components for a multiple number of transceiver modules are mounted or integrated, with the top surface of the silicon interposer used as a reference plane for defining the optical signal path between separate optical components. Indeed, by using a single silicon wafer as the platform for a large number of separate transceiver modules, one is able to use a wafer scale assembly process, as well as optical alignment and testing of these modules.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of co-pending U.S. patent applicationSer. No. 13/463,408, filed May 3, 2012, which is herein incorporated byreference.

TECHNICAL FIELD

The present invention relates to a wafer scale implementation ofopto-electronic transceivers and, more particularly, to the utilizationof a silicon wafer as an optical reference plane and platform upon whichall necessary optical and electronic components are assembled for amultiple number of transceivers in a wafer scale process.

BACKGROUND

In optical communication networks, transceivers are used to transmit andreceive optical signals over optical fibers or other types of opticalwaveguides. On the transmit side of the transceiver, a laser diode andassociated circuitry is used to generate a modulated optical signal(representing data) that is ultimately coupled into an output signalpath (fiber, waveguide, etc.). On the receive side of the transceiver,one or more incoming optical signals are converted from optical signalsinto electrical signals within a photodiode or similar device. Inasmuchas the electrical signal is very weak, an amplifying device (forexample, a transimpedance amplifier) is typically used to boost thesignal strength before attempting to recover the data information fromthe received signal.

Optical transceiver modules thus comprise a number of separatecomponents that require precise placement relative to one another. Asthe components are being assembled, active optical alignment is requiredto ensure that the integrity of the optical signal path is maintained.In most cases, these transceiver modules are built as individual unitsand, as a result, the need to perform active optical alignment on aunit-by-unit basis becomes expensive and time-consuming.

As the demand for optical transceiver modules continues to increase, theindividual unit assembly approach becomes problematic and, therefore, aneed remains for a different approach to optical transceiver assemblythat can improve the efficiency of the construction process whilepreserving the integrity of module, including the required preciseoptical alignment between elements.

SUMMARY OF THE INVENTION

The need remaining in the art is addressed by the present invention,which relates to a wafer scale implementation of an opto-electronictransceiver assembly process and, more particularly, to the utilizationof a silicon wafer as an optical reference plane and platform upon whichall necessary optical and electronic components are simultaneouslyassembled for a plurality of separate transceiver modules.

In accordance with the present invention, a silicon wafer is utilized asa “platform” (also referred to hereinafter as an interposer) upon whichall of the components for a multiple number of transceiver modules aremounted or integrated, with the top surface of the silicon interposerused as a reference plane for defining the optical signal path betweenseparate optical components. Indeed, a single silicon wafer is used asthe platform for a large number of separate transceiver modules,providing the ability to use a wafer scale assembly process, as well asoptical alignment and testing of these modules, addressing the concernsof the prior art as mentioned above.

In further accordance with the present invention, the utilization of asilicon interposer allows for various through-silicon vias to be formedand used to provide electrical connections between components placed onthe interposer and underlying electrical components. Electronicintegrated circuits such as laser drivers, micro-controllers andtransimpedance amplifiers are accurately placed on the siliconinterposer using photolithographically-aided features formed on theinterposer. Wafer scale wirebonding techniques are used to create thenecessary electrical connections between the individual elements.Optical components such as lasers, isolators, lenses (individual andarrays), photodiodes and the like are placed withinlithographically-defined openings on the interposer, where the abilityaccurately and precisely define the location and size of openings usingconventional CMOS fabrication techniques allows for passive opticalalignment processes to be used where appropriate.

It is an aspect of the present invention that the wafer scale assemblyof multiple transceiver modules allows for a wafer scale activealignment scheme to be used when necessary, based on an electro-opticprobe containing a precisely placed detector and/or optical source,turning mirrors and other optics, as well as electrical probes. Byvirtue of the wafer scale assembly of the transceiver modules, theplacement of components and subsequent alignment and testing can beperformed in a conventional “step and repeat” fashion.

In one embodiment of the present invention, a second wafer is used as a“lid” for the assembled modules, with the lid wafer first being etchedand processed to define separate cavities within which the individualtransceiver modules will be located. The lid may be formed of glass,silicon or any other suitable material. A wafer-to-wafer bonding of thearrangement results in creating the final wafer scale transceiverassembly, which can then be diced to create the separate, individualtransceiver modules.

In an alternative embodiment, a metal lid may be used in situations(high bandwidth, high frequency, for example) that have more stringentrequirements with respect to EMI shielding.

A particular embodiment of the present invention comprises a wafer scalearrangement of optical transceiver modules including a siliconinterposer wafer for use as a platform for assembling a plurality ofseparate transceiver modules, the silicon interposer wafer defined ascomprising a planar top surface defining an optical reference plane, aplurality of conductive vias formed therethrough to provide electricalconnections to other components and optical waveguiding regions formedalong the surface thereof and a dielectric layer formed over the planartop surface of the silicon interposer wafer, the dielectric layer forsupporting the placement and interconnection of electrical integratedcircuit components associated with a plurality of separate transceivermodules, the dielectric layer configured to include a plurality ofopenings formed therethrough so as to expose the planar top surface ofthe silicon interposer wafer in each opening, the plurality of openingsof predetermined size and disposed in predetermined locations forproperly positioning and aligning optical components of each transceivermodule, the dielectric layer further including electrical conductivepaths for providing electrical connection between the supportedelectrical integrated circuit components and selected ones of theconductive vias of the underlying silicon wafer.

Other and further aspects and advantages of the present invention willbecome apparent during the course of the following discussion and byreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, where like numerals represent likeelements in several views:

FIG. 1 illustrates an exemplary silicon wafer that may be used to form asilicon interposer for wafer scale assembly of multiple transceivermodules in accordance with the present invention;

FIG. 2 illustrates an exemplary arrangement of a combination of atransceiver module-populated silicon interposer wafer with a “lid”wafer, where the lid is ultimately bonded to the interposer wafer toform a packaging of multiple transceiver modules;

FIG. 3 is a cross-sectional view of an exemplary interposer dieincluding plurality of components formed in accordance with the presentinvention;

FIG. 4 is a cross-sectional view of an alternative interposer diestructure formed in accordance with the present invention, thisstructure including an opening to the silicon interposer surface to forman optical reference plane;

FIG. 5 is an isometric view of an exemplary interposer die showing aplurality of openings for supporting the various optical componentsforming the transceiver arrangement of the present invention;

FIG. 6 is a view of the arrangement of FIG. 5, in this case with theoptical and electrical components disposed on the surface of theinterposer die;

FIG. 7 is a detailed isometric illustration of an exemplary lens andphotodiode component that may be used to capture an incoming opticalsignal and convert it into an electrical representation;

FIG. 8 is a cut-away side view of the arrangement of FIG. 7;

FIG. 9 illustrates the interposer die as shown in FIG. 6, as well as anexemplary lid component that may be bonded to a fully-populatedinterposer wafer;

FIG. 10 is an alternative view of the arrangement of FIG. 9, in thiscase showing the underside of the lid component;

FIG. 11 illustrates an alternative embodiment of the present invention,in this case where a plurality of four separate laser diodes aredisposed on submounts, with the submounts then disposed in openingsformed in the interposer;

FIG. 12 shows yet another embodiment of the present invention, in thiscase where a simplified, single lens array is utilized to providefocusing for both the transmitting and receiving portions of the module;

FIG. 13 is a top view of the arrangement of FIG. 12;

FIG. 14 is another embodiment of the present invention where theintegrated circuits are stacked to form a “three-dimensional”configuration;

FIG. 15 is a top view of a stacked configuration of the presentinvention;

FIG. 16 is an isometric view of another embodiment of the presentinvention, in this case utilizing a metal lid to provide additional EMIshielding;

FIG. 17 is a side view of an exemplary embodiment using a metal lid, inthis case where the lid is formed to include interior walls to isolatethe components form the optical transmitter; and

FIG. 18 is a side view of an alternative embodiment of the presentinvention using a metal lid without any interior walls.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth in order to provide athorough understanding of the present invention. However, it will beapparent to one skilled in the art that the present invention may bepracticed in other embodiments that depart from these specific details.In other instances, detailed descriptions of well-known devices andmethods are omitted so as not to obscure the description of the presentinvention with unnecessary details.

As mentioned above, a significant improvement in fabrication efficiency,without sacrificing the integrity of the necessary precise opticalalignments between various individual elements, is provided inaccordance with the present invention by utilizing a wafer scaleassembly technique, employing a silicon wafer as a carrier substrate(also referred to hereinafter as an interposer) upon which theindividual components (including electronic integrated circuits, activeoptical devices and passive optical devices) are mounted, aligned,bonded, etc. Since a typical silicon wafer (for example, an 8″ wafer)can support the creation of multiple transceiver modules (e.g., tens ofdie across the wafer surface), the wafer-scale fabrication and assemblytechniques of the present invention are capable of improving theefficiencies of transceiver module assembly and packaging processes.

Prior to describing the details associated with using a silicon wafer asan interposer or platform, the following discussion, with reference toFIGS. 1 and 2, will provide an overall understanding of the benefits ofusing a wafer scale process to assemble the transceivers in the firstinstance.

FIG. 1 illustrates an exemplary silicon wafer 10 that may be utilized asan interposer wafer in accordance with the present invention. As shown,a large number of individual interposer die 12 are defined on wafer 10as being locations where individual transceiver modules are to beassembled. Once wafer 10 is fully populated with the multipletransceiver modules, a separate lid wafer 14, as shown in FIG. 2, isbonded to interposer wafer 10 in a manner that results in encapsulatingeach individual transceiver module. In particular, lid wafer 14 isformed to include separate chambers 16 that will form the coverings forthe separate transceiver modules (as described in detail below). Oncethe wafers are joined, the bonded structure is diced to form the final,individual transceiver modules. A laser dicing process is preferred, butit is to be understood that any other suitable process for separatingthe bonded wafers into separate transceiver modules may also be used.

With this understanding of the overall wafer-based approach to creatingtransceiver modules, the following discussion will focus on the aspectsassociated with utilizing a silicon interposer platform in the assemblyof exemplary transceiver embodiments. It is to be understood that indrawings where only a single transceiver arrangement shown, the actualassembly process creates multiple transceiver modules across the surfaceof the interposer wafer, at each separate die location (or at least at asubset of the die locations, as need be, based upon need, wafer qualityand the like), as shown in FIG. 1.

FIG. 3 is a cut-away side view of a portion of an interposer wafer 10,as processed to be populated with a number of components forming anexemplary transceiver module. In this 6 SIO-0203EA case, a buried oxide(BOX) layer 18 is formed over top surface 11 of interposer wafer 10,with a relatively thick interlevel dielectric (ILD) layer 20 formed overBOX layer 18. A relatively thin silicon layer 22 is created at theinterface between BOX layer 18 and ILD layer 20, where silicon layer 22is used as an optical waveguiding layer. Indeed, it is seen that thecombination of interposer wafer 10, BOX layer 18 and silicon layer 22forms a well-known silicon-on-insulator (SOI) optical structure that hasbeen extensively used in recent years in the creation of passive andactive optical components.

As will be discussed hereinbelow, optical waveguiding layer 22 isspecifically defined and is routed along this interface to provide thedesired optical communication path(s) between the various componentsforming a transceiver module. In accordance with the present invention,the planarity of top surface 11 of interposer wafer 10 is preciselycontrolled so that surface 11 functions as an optical reference planefor the transceiver module. As a result, and discussed in detail below,the creation of an optical reference plane allows for passive techniquesto be used to provide alignment between various optical components asthey process propagating optical signals. In an alternative embodiment,one or more optical components can first be assembled and preciselyaligned on a separate submount element, as discussed below in associatedwith FIG. 11, with the submount then precisely placed on surface 11 ofinterposer 10, avoiding the need to perform multiple wafer scale activealignments. Also shown in the view of FIG. 3 is alithographically-defined feature 24, which may be used for providingoptical I/O connections to interposer wafer 10.

Another advantage of utilizing interposer wafer 10 in the fabrication oftransceiver modules is that the necessary connections between theelectronic integrated circuit components forming the transceiver module(e.g., laser driver, transimpedance amplifier, etc.) and underlyingsources of power, signal, etc., can be created by using conventionalvias 26 formed through the thickness of interposer 10, as shown in FIG.3. Either metal or doped silicon material can be used to “fill” vias 26and form the conductive path between the transceiver module and thepower and signal contacts. In the specific embodiment shown in FIG. 3, aplurality of solder bumps 28 is formed at the termination of vias 26 andused for connection to an associated arrangement of bond pads on aprinted circuit board, or other source of power and data signals (notshown).

FIG. 4 is a side view of another embodiment of interposer wafer 10 andincluded components forming an optical transceiver module. Thisparticular embodiment does not specifically show BOX layer 18, but it isto be understood that such a layer may still be included in such atransceiver arrangement. Specifically shown in this view is theprocessing of ILD layer 20 to form a plurality of openings 30. Asdiscussed above, these openings 30 are created to expose top surface 11of silicon interposer wafer 10, allowing surface 11 to function as awell defined optical reference plane. Advantageously, it is possible touse standard photolithographic patterning and etching techniques to formopenings 30 with precise geometries and in precise locations relative toother components forming the transceiver so as to provide for passiveoptical alignments, where possible, between various components. Indeed,a selective etchant (such as HF, for example) will naturally stop atsurface 11 of silicon interposer 10 as predefined regions of ILD layer20 are removed. Therefore, there is no concern about either over-etchingor under-etching and degrading the planarity of surface 11 during theetching process.

FIG. 5 is an isometric top view of an exemplary interposer die 12particularly illustrating the creation of a plurality of openings 30 forsupporting the various optical components in the predefined, preciselocations by virtue of using exposed surface 11 of interposer 10 as areference plane. While FIG. 5 shows only a single interposer die, it isto be understood that the process of forming these openings, followed bythe placement of the various components, is performed as a wafer scaleprocess, where each interposer die 12 of wafer 10 is simultaneouslypopulated with the individual optical and electrical components. In theparticular embodiment of FIG. 5, a plurality of openings 30 are formedto allow for the precise placement of a number of critical opticalcomponents. As described above, openings 30 are created to expose topsurface 11 of silicon interposer 10, where surface 11 is preciselydefined and controlled to create and maintain a planar opticalreference. For example, a first opening 30-1 is used as the location fora laser diode and a second opening 30-2 is used to support a lenselement.

Through the careful control of the location of openings 30-1 and 30-2(possible using conventional photolithographic patterning and etchingtechniques), once the laser diode and lens are inserted in theirrespective openings, they will be aligned, since each component will beresting on optical reference plane top surface 11. Similarly, a thirdopening 30-3 is used to support an optical isolator, which will thenalso be in the optical signal path and in alignment with the laser diodeand lens. In some cases, active alignment is required to properly alignthe laser diode with its associated lens. In that event, a wafer scaleactive alignment scheme is used, based, for example, on an electro-opticprobe comprising a precisely placed detector and/or optical source,turning mirrors and other optics (and, perhaps, electrical probes) toprovide alignment and testing of components in a conventional “step andrepeat” fashion across the wafer surface. Similarly, wafer scaleelectrical burn-in of various components (such as, for example, a laserdiode) is accomplished using an electrical probe card in the same stepand repeat process.

Continuing with the description of FIG. 5, an opening 30-4 is createdthrough ILD layer 20 to support a lens element, with a large opening30-5 positioned behind opening 30-4. Large opening 30-5 is used tosupport a product-specific CMOS photonic integrated circuit used toperform various types of signal processing (e.g., modulating a CW lasersignal with an electrical data signal to create a data-modulated opticaloutput signal). The particular operation of the photonic integratedcircuit is not germane to the subject matter of the present invention.An opening 30-6 is used to support a coupling element associated with anoutput optical signal, with opening 30-7 utilized to support anassociated optical I/O connection (see, for example, feature 24 as shownin FIG. 3). A number of vias 26 are also shown in FIG. 5, where in thisparticular embodiment the vias are disposed in a regular grid patternacross the surface of the complete silicon interposer wafer 10 so thatthey may be used as needed in different transceiver configurations.

FIG. 6 is a view of the arrangement of FIG. 5, in this case with thevarious optical components disposed within their associated openings. Asshown, a laser diode 32 is positioned within opening 30-1 and a microlens 34 is disposed within opening 30-2. An isolator 36 is placed withinopening 30-3, in the optical output signal path from laser diode 32. Theoutput from isolator 36 is then passed through a micro lens array 38disposed within opening 30-4, where the lens array is used to couple thepropagating optical signal into a CMOS photonic integrated circuit 40.Various well-known methods may be used for affixing the opticalcomponents in place in their respective openings. In particular, epoxy,eutectic bonding or other arrangements may be used to permanently attachthe optical components in their respective openings. It is to beunderstood that an appropriate temperature hierarchy needs to first beestablished such that the stability of the joints are ensured duringother potentially high temperature post-processing operations.

In the specific embodiment shown in FIG. 6, a fiber array connector 42is disposed within opening 30-7, with the individual fibers 44 formingthe array used to introduce optical signals to, and output opticalsignals from, the transceiver module. It is to be noted that opening30-7 may, in some cases, comprise feature 24 that is lithographicallyformed in manner described above. In this embodiment, a lens array 46 isincluded within fiber array connector 42 at the termination of theplurality of individual fibers 44. In operation, incoming opticalsignals along, for example, optical fibers 44-1 and 44-2 will passthrough lens array 46, and then impinge a lens element 48 and photodiode 50 disposed within opening 30-6, creating an associated electricalsignal representation. Lens element 48 and photodiode 50, as shown inFIG. 6, are disposed in opening 30-6, which is formed to be in alignmentwith opening 30-7 (and, more particularly, with the location of fibers44-1 and 44-2 within the array). Various electrical components, such astransimpedance amplifier 33 and a laser driver 35 are also positioned atpredetermined locations on interposer die 12. Here, the electricalcomponents are disposed on the surface of ILD layer 20 (see FIG. 4),with necessary electrical connections made using the vias 26 formedthrough interposer die 12.

An exemplary combination of lens element 48 and photodiode 50 is shownin FIGS. 7 and 8, where FIG. 7 is an isometric view, and FIG. 8 is acut-away side view. In this particular embodiment, lens element 48 takesthe form of a lens array and includes a plurality of curved surfaces 52for focusing a plurality of incoming optical signals, as best shown inFIG. 8. A prism component 54 is used as a 90° turning mirror to redirectthe plurality of focused optical signals from a horizontal to a verticalplane, with photodiode 50 (in this case a photodiode array) disposed toreceive incoming optical signals. It is to be understood that this ismerely one exemplary configuration for receiving incoming opticalsignals and converting them into an electrical representation. Variousother arrangements may be utilized within the wafer-based arrangement oftransceiver modules in accordance with the present invention.

Referring back to FIG. 6, a sealing layer 56 is shown as being formedaround the perimeter of interposer die 12 (again, it is to be understoodthat this layer is formed around the perimeter of each die 12 forminginterposer wafer 10). This sealing layer, which may comprise a glassfrit material, a AuSn solder, or any other suitable material, is used tobond a separate lid component to the populated interposer die. Inaccordance with the present invention, and shown below in FIG. 9, a lidcomponent 58 is formed to match the “footprint” of interposer die 12 andis disposed over die 12 and sealed thereto by the presence of sealinglayer 56. Recalling the discussion associated with FIG. 2, it is to beunderstood that a plurality of separate lid components 58 are formed ina separate wafer and, during fabrication, the entire wafer is bonded(via the multiple sealing layers 56) to interposer wafer 10.

Turning to FIG. 9, it is evident that lid component 58 is specificallyformed to follow the periphery of interposer die 12 as guided by thepattern of sealing layer 56. Bottom surface 60 of lid component 58 iscoated with a specific material (for example, a metal such as gold) toform a sealing of lid component 58 to interposer die 12. As shown inFIG. 9, sealing layer 56 and lid component 58 are specifically designedto create an opening 62, which allows for the optical input and outputsignals to access the transceiver module (for example, opening 62 may beused to allow for optical connector 42 to be inserted, as shown in thisparticular embodiment). FIG. 10 is an alternative isometric view of thearrangement of FIG. 9, showing in particular bottom surface 60 of lidcomponent 58 and illustrating how it follows the same path as sealinglayer 56 of interposer die 12.

As mentioned above, an advantageous feature of utilizing a silicon waferinterposer for assembling, aligning and testing transceiver modules on awafer-scale basis is that the silicon interposer may easily befabricated to accommodate various arrangements of the differentcomponents forming the transceiver. Indeed, some arrangements may usemultiple laser inputs, external laser inputs, or other variousembodiments. FIG. 11 illustrates another embodiment of the presentinvention where in this case, a set of four separate laser diodes 32-1,32-2, 32-3, and 32-4 are included within the transceiver. As shown inFIG. 11, each laser diode is positioned with an associated lens 34-i andisolator 36-i on a submount element 64. The use of submounts 64 allowsfor the optical transmitting subassembly comprising the laser, isolatorand lens to be separately mounted and aligned. Thereafter, the set ofsubmounts 64 are disposed in properly-sized openings formed ininterposer die 12 (not visible in the view of FIG. 11), where the properplacement of the openings for these submounts results in creating thedesired optical alignment with an associated fiber array 66. In anexemplary embodiment, the submount may comprise a thermo-electric cooler(TEC) component. An exemplary lid component 68 is also shown in FIG. 11,where it is to be understood that lid component 68 is formed to have adepth sufficient to accommodate the raised positioning of the laserdiodes.

FIGS. 12 and 13 illustrate yet another embodiment of the presentinvention, in this case where interposer die 12 is processed to form asingle opening 70 for placement of a lens array 72 that is used inconjunction with both transmit and receive optical signals (compare withopenings 30-4 and 30-6 in FIG. 5, as used to support separate lenselements 38 and 48, respectively). Again, it is a particular advantageof the utilization of a silicon wafer interposer as a “platform” for theassembly of optical transceiver modules that the specific arrangementand placement of components can be modified by merely changing thepatterning of ILD layer 20 to provide the desired openings (of theproper dimensions) in the locations associated with a particulartransceiver module arrangement, while always maintaining the opticalreference plane defined by top surface 11 of interposer wafer 10. FIG.12 is an isometric view of die 12, illustrating the location of opening70 and lens array 72 with respect to both laser diode 32 and fiberconnector 42. Input optical signal I from laser diode 32 is shown aspassing through lens array 72 and entering an integrated transceivercircuit arrangement 74. A set of four output signals O is shown in thisexample as exiting integrated transceiver circuit arrangement 74 andpassing through lens array 72 so as to be focused into a set of fibers44 within fiber connector 42. The location of the input and outputoptical signals is best seen in the view of FIG. 13.

Another embodiment of the present invention is shown in FIG. 14, whichcan be thought of as a “three dimensional” transceiver module, where afirst integrated circuit is stacked vertically on a second integratedcircuit. As shown, a first integrated circuit 76 is defined as anopto-electronic integrated circuit 76 and is responsive to an incomingoptical signal to create a modified optical output signal. A secondintegrated circuit 78 is defined as an electronic integrated circuit andprovides power and electrical data signals to opto-electronic integratedcircuit 76. Electronic integrated circuit 78 is, itself, electricallycoupled to interposer die 12. As discussed above in association withFIG. 3, interposer die 12 includes a plurality of silicon through vias26 which enable the transfer of electrical signals from an associatedprinted circuit board (not shown) generally disposed underneathinterposer 10 and the specific components of the transceiver module.Again, the specific locations of the openings formed through ILD layer18 is dictated by the various components used to form the transceivermodule.

It is a particular advantage of using a silicon interposer with thestacked arrangement of FIG. 14 that a multi-level metallization withinILD layer 20 (as shown in FIG. 3) can be used to provide a large numberof interconnections to different circuits within a minimal space on theinterposer die itself (i.e., a “high density” arrangement). FIG. 15 is atop view of an alternative three-dimensional, stacked transceiverembodiment, where at least some of the associated optical components (inthis case, a plurality of optical modulators 80) are formed within thesilicon waveguiding layer 22 of interposer 10. Monolithic (or hybrid)inclusion of photodiodes 82 within wave guiding layer 22 is alsopossible. Indeed, the ability to integrate various silicon-basedcomponents of an optical transceiver directly into the wave guidinglayer is another advantage of utilizing a silicon interposerlayer—processed at a wafer-scale level—in accordance with the presentinvention. Also shown in this view is a lithographically-defined feature86 that provides “end fire” coupling of optical signals into waveguidinglayer 22. In a preferred embodiment, the end terminations of the waveguiding layers are formed as nanotapers to improve coupling efficiency.

In some applications of systems utilizing transceivers formed in themanner described above, the performance of high speed, high frequencysignals is adversely impacted by the presence of electro-magneticinterference (EMI). In the above-described arrangements, an additionalground pad (or ring) was required to be formed on interposer die 12 andthen connected to a ground plane.

An alternative solution, formed in accordance with the presentinvention, is shown in FIG. 16, where a metal lid component 90 isutilized in place of the silicon lids as discussed above. Referring toFIG. 16, sealing layer 56 is formed as a metal that will assist informing a ground connection with metal lid component 90. In thisparticular embodiment, an additional grounding path 57 is formed toencircle the optical transmitting components 32, 34 and 36, which aremost sensitive to EMI. In this embodiment, “grounding” is provided byutilizing a special via 92 within interposer die 12 that is positionedto contact a portion of metal lid 90 and provide an electricalconnection to a ground plane (not shown) located under interposer die12. FIG. 17 is a simplified side view of this arrangement showing theinterconnection of metal lid 90 and a ground plane 94 through via 92 ofinterposer die 12. A side view of an alternative embodiment using ametal lid 90 is shown in FIG. 18, where this embodiment does not includea separate shielding configuration around the optical transmittingcomponents.

It is to be understood that the embodiments of the present invention asdescribed above are intended to be exemplary only. The scope of thepresent invention is therefore intended to be limited only by the scopeof the claims appended hereto.

We claim:
 1. A method for aligning components of a plurality of opticaltransceiver modules in a wafer scale arrangement, comprising: using asilicon interposer wafer as a platform for assembling a plurality ofseparate transceiver modules, wherein the silicon interposer wafercomprises a planar surface defining an optical reference plane, aplurality of conductive vias formed therethrough to provide electricalconnections to other components, and optical wave guiding regions formedalong the planar surface; forming a dielectric layer over the planarsurface of the silicon interposer wafer, wherein the dielectric layer isconfigured to support the placement and interconnection of electricalintegrated circuit components associated with the plurality of separatetransceiver modules, the dielectric layer further including electricalconductive paths for providing electrical connection between thesupported electrical integrated circuit components and selected ones ofthe conductive vias of the underlying silicon interposer wafer;patterning and etching the dielectric layer to create a plurality ofopenings, thereby exposing the planar surface of the silicon interposerwafer at each opening, wherein the plurality of openings are ofpredetermined size and are disposed in predetermined locations forproperly positioning and aligning optical components of each transceivermodule to permit optical signal paths between the aligned opticalcomponents along the optical reference plane; and assembling theplurality of separate transceiver modules on the silicon interposerwafer.
 2. The method of claim 1, wherein the plurality of openings arecreated using a preferential etchant, such that the etching processstops upon exposure of the underlying silicon interposer wafer.
 3. Amethod for assembling an optical transceiver module, the methodcomprising: using a silicon interposer wafer as a platform, wherein thesilicon interposer wafer comprises a planar surface defining an opticalreference plane and a dielectric layer formed over the planar surface;forming a plurality of openings through the dielectric layer, therebyexposing the planar surface of the silicon interposer wafer at eachopening; and positioning optical components of the optical transceivermodule within the plurality of openings, thereby aligning the opticalcomponents and establishing optical signal paths along the opticalreference plane between aligned optical components.
 4. The method ofclaim 3, wherein a plurality of optical transceiver modules are formedin a wafer scale assembly using a common silicon interposer wafer. 5.The method of claim 4, wherein the plurality of openings are formed bypatterning and etching the dielectric layer in predetermined areasassociated with the placement of the optical components of the pluralityof optical transceiver modules formed in the wafer scale assembly. 6.The method of claim 4, further comprising attaching a lid component tothe combination of the silicon interposer wafer and the dielectric layerand disposed over the optical transceiver modules, the lid componentconfigured to include a plurality of chambers associated with theplurality of optical transceiver modules such that each opticaltransceiver module is separately encapsulated.
 7. The method of claim 6,wherein attaching the lid component comprises bonding the lid componentto the combination of the silicon interposer wafer and the dielectriclayer.
 8. The method of claim 6, wherein each optical transceiver moduleas formed includes a sealing layer defining the outline thereof, thesealing layer used to attach an associated portion of the lid component.9. The method of claim 8, wherein a bottom surface of the lid componentis covered with a material that creates a permanent attachment to thesealing layer when the lid component is attached to the combination ofthe silicon interposer wafer and dielectric layer.
 10. The method ofclaim 6, wherein the lid component comprises one of a silicon wafer anda glass wafer.
 11. The method of claim 6, wherein the lid componentcomprises a metal component.
 12. The method of claim 11, furthercomprising coupling the lid component to an associated ground planeusing a grounding via formed through the dielectric layer and thesilicon interposer wafer.
 13. The method of claim 12, wherein the lidcomponent includes an internal compartment within each chamber, theinternal compartment for separately encapsulating the optical portion ofeach optical transceiver module, providing protection fromelectromagnetic interference.
 14. The method of claim 3, wherein a setof openings formed through the dielectric layer are associated withoptical input/output connections for the optical transceiver modules.15. The method of claim 14, wherein the set of openings are disposed atan end region of each optical transceiver module location such that anoptical connector is capable of accessing the optical components and isaligned with the optical plane reference surface of the siliconinterposer wafer.
 16. The method of claim 3, wherein each opticaltransceiver module includes optical transmitting components including alaser diode, a lens element, and an optical isolator, and the dielectriclayer is formed to include openings for the laser diode, lens element,and optical isolator in each region associated with a separatetransceiver module, wherein a set of openings for a laser diode, lenselement, and optical isolator in each region are formed to provideoptical alignment therebetween, with the laser diode disposed in a firstopening, the lens element disposed in a second opening, and the opticalisolator disposed in a third opening of the dielectric layer.
 17. Themethod of claim 16, wherein a single lens element is utilized with bothtransmitting and receiving optical signals, the single lens elementcomprising a lens array and disposed in an opening in the dielectriclayer positioned to align with both the optical transmitting andreceiving components.
 18. The method of claim 3, wherein each opticaltransceiver module includes optical transmitting components including alaser diode, a lens element, an optical isolator, and a submountcomponent, the laser diode, lens element and optical isolator beingattached to a surface of the submount component in an alignedconfiguration, the submount component being disposed within an openingformed through a predetermined area of the dielectric layer.
 19. Themethod of claim 3, wherein each optical transceiver module includesoptical receiving components including a lens element and a photodiode,and the dielectric layer is formed to including openings for the lenselement and the photodiode in each region associated with a separatetransceiver module, the openings being configured to provide opticalalignment between an incoming optical signal, the photodiode and thelens element.
 20. A method for aligning components of an opticaltransceiver module, the method comprising: positioning opticalcomponents of the optical transceiver module within a plurality ofopenings formed through a dielectric layer, thereby establishing opticalsignal paths between aligned optical components and along an opticalreference place, wherein the optical reference plane is defined by aplanar surface of a silicon interposer wafer, the dielectric layer isdisposed over the planar surface, and each opening through thedielectric layer exposes the planar surface.